Astronomy Picture of the Day |
APOD: 1998 July 12 - Asteroid Gaspra's Best Face
Explanation:
Asteroid
951 Gaspra is a huge rock tumbling in space.
Gaspra became one of the best-studied
asteroids in 1991 when the
spacecraft Galileo flew by.
In the
above photograph, subtle color variations have been
exaggerated to highlight changes in reflectivity,
surface structure and composition. Gaspra is about 20 kilometers long and orbits the
Sun in the
main asteroid belt between
Mars and
Jupiter.
APOD: 1999 August 7 - Ida and Dactyl: Asteroid and Moon
Explanation:
This asteroid has a moon!
The robot spacecraft Galileo
currently exploring the Jovian system, encountered and photographed two
asteroids
during its long journey to Jupiter.
The second asteroid it photographed,
Ida, was discovered to have
a moon which appears as a small dot to the right of Ida in
this picture.
The tiny moon, named Dactyl, is about one mile across, while
the potato shaped Ida measures about 36 miles long and 14 miles wide.
Dactyl is the first moon of an asteroid ever discovered.
The names Ida and Dactyl are based on characters in
Greek mythology.
Do other asteroids have moons?
APOD: 1998 March 16 - Asteroids in the Distance
Explanation:
Rocks from space hit Earth every day.
The larger the rock, though, the less often Earth is struck.
Many kilograms of space dust pitter to Earth daily.
Larger bits appear initially as a bright meteor. Baseball-sized rocks and ice-balls
streak through our atmosphere daily,
most evaporating quickly to nothing.
Significant threats do exist for rocks near
100 meters in diameter,
which strike Earth roughly every 1000 years.
An object this size could cause significant
tidal waves were it to strike an ocean,
potentially devastating even distant shores.
A collision with a
massive asteroid,
over 1 km across,
is more rare,
occurring typically millions of years apart, but
could have truly global consequences.
Many asteroids remain undiscovered.
In fact, the discovery of several was announced
last week; one is shown as the long blue streak in the
above photograph.
Such an
interplanetary collision
would not affect Earth's orbit so much as raise dust
that would
affect Earth's climate.
One likely result is a global extinction of
many species of life,
possibly dwarfing the ongoing
extinction occurring now.
Authors & editors:
Robert
Nemiroff
(MTU)
& Jerry Bonnell (USRA)
NASA Technical Rep.:
Jay Norris.
Specific rights apply.
A service of:
LHEA at
NASA/
GSFC
&
Michigan Tech. U.